IB Biology B2.2 Organelles and Compartmentalization HL

What are organelles?

Discrete structures in cells that are adapted to perform one or more vital specialized function

Name 3 no membrane organelles

ribosomes, centrioles, microtubules

Name 3 single membrane organelles

vesicles, plasma membrane, golgi apparatus

Name 3 double membrane organelles

nuclei, mitochondria, chloroplasts

Name 3 structures that are NOT organelles

Cell walls - outside plasma membrane, extracellular

Cytoskeleton - narrow protein filaments not discrete enough

Cytoplasm - not discrete, liquid

In eukaryotes, keeping what inside the nucleus _____ the ___

chromosomes, safeguards, DNA

Summarized process of Protein synthesis

DNA, transcription in nucleus, mRNA (copied portion), translation in cytoplasm using ribosome, protein

What's another advantage to having a SEPARATED nucleus besides protection of DNA?

When DNA is used to make mRNA, it can be modified before its translated into proteins, extra step

What are the 3 advantages to compartmentalization in the cytoplasm of eukaryote cells?

1. Enzymes and substrates can be concentrated

2. Substances that cause damage to the cell can be contained in a organelle membrane. Ex. Digestive enzymes in lysosomes could kill a cell if not stored properly

3. pH can be maintained at an ideal level for certain processes, which can vary for others. Ex. Paramecium feed by endocytosis, and the pH inside the vacoule drops and rises to provide optimal conditions for digestion.

Mitochondria produce ______

ATP by cellular respiration

What are some characteristics of mitochondria? [3]

Double membrane, inner membrane has infoldings called cristae, fluid filling the inside is called the matrix

What are the 3 adaptions of mitochondria?

1. Inner mitochondrial membrane is the site of OXIDATIVE PHOSPHORYLATION, and cristea are innner membrane projections that INCREASE THE SURFACE AREA for this process to occur

2. SMALL VOLUME of intermembrane space that allows high concentrations of protons to build up in the gradient faster

3. MATRIX FLUID compartmentalizes the enzymes and allows them to perform more quickly

Chloroplasts produce ___

glucose through photosynthesis

What are some characteristics of chloroplasts? [3]

Double membrane without infoldings, extensive system of internal membranes called thylakoids, small fluid filled spaces, fluid filing the chloroplasts is stroma

What are the 3 adaptions of chloroplasts? [3]

1. Thylakoid membranes contain pigment arranged in photosystems that absorb light. LARGE SURFACE AREA allows pigment to absorb light

2. Proton gradient is needed, the SMALL VOLUME of fluid allows gradient to build quickly

3. The fluid of the STROMA COMPARTMENTALIZES and allows it to be performed quickly

Detail the first functional benefit of the nucleus' double membrane

(enter and exits) [4 pts]

- The nucleus has a double membrane with large pores that allow large molecules to pass through, unlike channel proteins.

- Double membrane allows inner and outer to connected to form a circular hole lined with proteins that control proteins that pass

Proteins made in the cytoplasm need to be able to ENTER the nucleus in order to form structure of chromosomes and regulate gene expression

mRNA and Ribosomes need to EXIT through the pores to enter the cytoplasm

Detail the second functional benefit of the nucleus' double membrane

-Double membrane allows it to break down into vesicles during meiosis and mitosis/cell division

-During cell division, the membrane breaks down allowing the chromosmes to be moved to the poles of the cell the membrane reforms

-Vesicles of a membrane can bud off and be moved to the side of the cell ready to re-form

Brief two functional benefits of double nuclear membrane

- Pores lined with proteins allow large molecules like other proteins to enter and mRNA and ribosomes to exit.

-Membrane can break down into vesicles to split the cell

What are ribosomes made up of ?

Ribosomes are made up of one large large and one small subunit consisting of rRNA and proteins.

What are free ribosomes?

Ribosomes not attached to membranes in the cytoplasm. Protiens synthesized by free ribosomes are retained in the cell either cytoplasm or nucleus

What are membrane-bound ribosomes?

Ribosomes that become attached to the rER. rER has cisternae/flattened sacs, and proteins synthesized by these ribosomes can be transferred elsewhere in the cell by a vesicle that buds of rER to go to the golgi apparatus. Proteins are used for TRANSPORT and secretion

What does the golgi apparatus do?

Processes polypeptides from the rER

What are the 4 steps to protein synthesis in the golgi apparatus?

1. Proteins are transported from the rER in vesicles

2. Enzymes in the cisternae change the polypeptide (adding carbs to make glycoproteins)

3. Protein moves through cisternae from the cis to trans side

4. After processing, the protein is transported in a vesicle from the golgi apparatus. If it's being secreted, the destination is the plasma membrane.

What are vesicles?

Rounded sacs made of a single membrane and material inside of it. They are small and dynamic structures that are continuously made, moved, and merged.

What is clathrin?

A three-legged protein that helps pinch off membrane. They bind together to form a lattice which helps the plasma membrane become indented and detach to form a sphere with a clathrin cage.